In many industries, like the petrochemical and chemical industries, contact of reaction fluids with a catalyst in a reactor under suitable temperature and pressure conditions effects a reaction between the components of one or more reactants in the fluids. Most of these reactions generate or absorb heat to various extents and are, therefore, exothermic or endothermic. The heating or chilling effects associated with exothermic or endothermic reactions can positively or negatively affect the operation of the reaction zone. The negative effects can include among other things: poor product production, deactivation of the catalyst, production of unwanted by-products and, in extreme cases, damage to the reaction vessel and associated piping. More typically, the undesired effects associated with temperature changes will reduce the selectivity or yield of products from the reaction zone. The heating of reactants may be useful for a variety of exothermic and endothermic processes. Dehydrogenation processes represent one class of endothermic processes that particularly benefit from indirect reaction zone heating to maintain a desired temperature profile.
This invention is particularly suited for exothermic processes. Exothermic reaction processes encompass a wide variety of feedstocks and products. Moderately exothermic processes include methanol synthesis, ammonia synthesis, and the conversion of methanol to olefins, phthalic anhydride manufacture by naphthalene orthoxylene oxidation, acrylonitrile production from propane or propylene, acrylic acid synthesis from acrolein, conversion of n-butane to maleic anhydride, the production of acetic acid by methanol carbonylation and methanol conversion to formaldehyde. Oxidation reactions generally represent a class of highly exothermic reactions. The exothermic nature of these reactions has led to many of these reactions incorporating a cooling system into the reactor design. Those skilled in the art routinely overcome the exothermic heat production with quench or heat exchange arrangements. Extensive teachings detail methods of indirectly exchanging heat between the reaction zone and a cooling medium. The art currently relies heavily on tube arrangements to contain the reaction and supply indirect contact with the cooling medium. The geometry of tubular reactors poses layout constraints that require large reactors and vast tube surface to achieve high heat transfer efficiencies.
Other process applications accomplish indirect heat exchange with thin plates that define channels. The channels alternately retain catalyst and reactants in one set of channels and a heat transfer fluid in adjacent channels for indirectly heating or cooling the reactants and catalysts. Heat exchange plates in these indirect heat exchange reactors can be flat or curved and may have surface variations such as corrugations to increase heat transfer between the heat transfer fluids and the reactants and catalysts. Many hydrocarbon conversion processes will operate more advantageously by maintaining a temperature profile that differs from that created by the heat of reaction. In many reactions, the most beneficial temperature profile will be obtained by maintaining substantially isothermal conditions. In some cases, a temperature profile directionally opposite to the temperature changes associated with the heat of reaction will provide the most beneficial conditions. For such reasons it is generally known to contact reactants with a heat exchange medium in cross flow, cocurrent flow, or countercurrent flow arrangements. A specific arrangement for heat transfer and reactant channels that offers more complete temperature control can be found in U.S. Pat. No. 5,525,311; the contents of which are hereby incorporated by reference. Other useful plate arrangements for indirect heat transfer are disclosed in U.S. Pat. No. 5,130,106 and U.S. Pat. No. 5,405,586.
Isolating reactants from coolants at the inlets and outlets of a plate exchanger arrangement leads to elaborate designs and intricate manufacturing procedures. Simplification of the fluid transfer at the inlets and outlets of a plate exchanger arrangement improves the cost effectiveness of and practicality of such arrangements in many processes.
It is, therefore, an object of this invention to simplify plate exchanger arrangements for the cooling of an exothermic reaction zone by indirect heat transfer.
It is a further object of this invention to simplify the feed and recovery of reactants and coolants from a heat exchange reactor using narrow channels.